Boston Marathon bombings and the aftermath

Members of the media wait outside federal court, Wednesday, March 4, 2015, in Boston, on the first day of the federal death penalty trial of Boston Marathon bombing suspect Dzhokhar Tsarnaev.

Members of the media wait outside federal court, Wednesday, March 4, 2015, in Boston, on the first day of the federal death penalty trial of Boston Marathon bombing suspect Dzhokhar Tsarnaev. (Michael Dwyer / AP)

A police dog sniffs near news cameras outside of the entrance to the John Joseph Moakley United States Courthouse during the first day of the Dzhokhar Tsarnaev trial on March 4, 2015 in Boston.

A police dog sniffs near news cameras outside of the entrance to the John Joseph Moakley United States Courthouse during the first day of the Dzhokhar Tsarnaev trial on March 4, 2015 in Boston. (Scott Eisen / Getty Images)

Members of a police honor guard lead a column of law enforcement officials into a memorial service for fallen Massachusetts Institute of Technology police officer Sean Collier, in Cambridge, Mass.

Members of a police honor guard lead a column of law enforcement officials into a memorial service for fallen Massachusetts Institute of Technology police officer Sean Collier, in Cambridge, Mass. (Steven Senne / Associated Press)